1. Field of the Invention
The invention relates to a wood treating agent and to a method of treating wood or wood-based materials or the like. More specifically, the invention relates to wood or a wood-based material or the like and to a use of photocatalysts to degrade organic substances, organic compounds and/or biocides.
2. Description of Related Art
The chemical protection of wood or wood-based materials or the like is accomplished by means of wood preservatives containing biocides. These preservatives are applied to the wood or are introduced into the wood and set up in it very long-lasting biocidal barriers to fungi and insects, which destroy wood. Wood or wood-based materials or the like may also contain organic substances and/or organic compounds.
The introduction of a wood preservative into the wood is performed by, for example, what are referred to as surface treatment processes such for example as brushing, dipping or spraying or by protracted exposure processes such for example as soaking in a tank or by impregnation processes such for example as impregnation in a pressurized vessel. What all these processes have in common is that the wood preservative makes its way into the interior of the wood via the surface thereof and, depending on the process selected, leaves behind it or creates, over a greater or lesser depth, a biocide-charged barrier zone or a barrier zone which is charged with organic substances and/or organic compounds. Within the barrier zone, the distribution of the organic substances and/or organic compounds and/or biocides, which will all also be referred to below as materials, is approximately uniform only in the case of the above-mentioned impregnation processes. In the case of the surface treatment processes and protracted exposure processes there is, as a rule, an exponential decrease in the content of the above-mentioned materials, which is also referred to as the active principle content, inwards from the surface.
In the case of the surface treatment processes, the depth of penetration of the wood preservative is usually approximately 1 to 5 mm and the depth over which it is effective, referred to above as the barrier zone, is usually 0.5 to 3 mm, there being a sharp exponential decrease in the distribution of the above-mentioned materials, and in particular in the biocide distribution, inwards from the surface in the barrier zone.
In the case of the protracted exposure processes, the depth of penetration of the wood preservative is usually approximately 5 to 15 mm, and the depth over which it is effective is 3 to 12 mm, there being a moderate exponential decrease in the distribution of the above-mentioned materials, and in particular in the biocide distribution, inwards from the surface in the barrier zone.
In the case of the impregnation processes, the depth of penetration of the wood preservative is usually more than 20 mm and the depth over which it is effective is likewise more than 20 mm, the distribution of the above-mention materials, and in particular the biocide distribution, being almost uniform in the barrier zone.
Particularly in the above-mentioned surface treatment processes but also in the protracted exposure processes, very high concentrations of the above-mentioned materials occur on and immediately below the treated surface of the wood or wood-based material or the like. The concentration gradient between the surface of the wood and the immediate surroundings causes a transmission of materials from the wood into the surrounding air or onto the suspended matter contained in the air. In enclosed spaces, additional pollution of the air in the spaces by biocides may occur particularly as a result of the desorption of biocide molecules from dust particles. Even if the desorption effects mentioned are only slight, it is desirable for them to be prevented at least in the area directly surrounding dwellings, in order to limit the total biocidal pollution in the immediate environment in which people live or they stay for short periods to a level which is feasible in technical terms. The high biocide concentration on wood surfaces is also a problem wherever treated wood comes into direct contact with humans or animals (patio decking, playgrounds, animal stalls, etc.). Much the same applies to pollution by individual ones or all of the materials mentioned above.